Transistors are widely used as an important electronic element (electronic part) constituting televisions or computers. At the present time, the transistors are produced using an inorganic material such as silicon. Recently, organic transistors having an organic element have received a great deal of attention (Non-Patent Document No. 1). The organic transistors can be formed by a wet-process such as a printing method. Therefore, a vacuum device, which is expensive and necessary to process silicon transistors, is not necessary. Due to this, production cost including facility investment can be dramatically reduced. In addition, processes can be carried out at low temperatures, and organic transistors can be formed on a plastic substrate. Therefore, organic transistors are thought to be an essential item in ubiquitous ages, that is, an essential component for achieving terminals having flexibility and low cost.
The organic transistor is an organic semiconductor element having essentially three electrodes, an insulating layer, and a semiconductor layer. As a production method for the electrode layer, the insulating layer, and the semiconductor layer, which form the organic semiconductor element, a wet-process such as a printing method and a dry-process such as a sputtering method can be exemplified. Among these, from the viewpoint of low-cost, a wet-process is preferable (Non-Patent Document No. 2).
In addition, as a method for improving the characteristics of the organic transistor, in order to improve crystallinity of the organic semiconductor layer making a channel formation area, a method has been suggested in which the surface of the gage insulating layer is treated with a surface treatment agent such as a silane coupling agent, and the channel formation area is formed thereon using organic semiconductor materials (Non-Patent Document No. 3 and Patent Document No. 1).
However, an ideal method for completely covering the surface of the substrate with a silane coupling agent without gaps inevitably increases liquid repellency of the surface of the insulating film. Due to this, it was difficult to form an organic semiconductor film having uniformity on the surface to be treated using an organic semiconductor solution. In the past, silane coupling agents used were limited, treatment conditions were limited, and the solvent used was also limited to carry out the surface treatment. In other words, when the conventional treatment methods are used, not only are the characteristics of the transistor produced limited, but also the solvent used is limited. Therefore, the wet-process is limited naturally. Due to this, it is difficult to produce a transistor having a large area and flexibility for practical use.
Examples of an organic semiconductor solution containing resin include a blend solution in which P3HT (poly(3-hexylthiophene)), PQT-12 (poly[5,5′-bis (3-dodecyl-2-thienyl)-2,2′-bithiophene]), or polymethyl methacrylate is dissolved in dichlorophenol. It is well-known that when the blend solution is spin-coated on the silicon oxide insulation film of which the surface is treated with a silane coupling agent, PMMA, which acts as a protective layer, is voluntarily separated as a layer, and forms a layer separation structure covering the organic semiconductor layer formed on the silicone oxide (Non-Patent Document No. 4). However, Non-Patent Document No. 4 does not disclose that a fluorine-based surfactant is added, and performance of the transistor can be improved.